Causes execution to cease and become dormant for approximately the seconds of real time indicated by seconds, whereupon execution is resumed.

Examples:

(sleep 1) => NIL
;; Actually, since SLEEP is permitted to use approximate timing,
;; this might not always yield true, but it will often enough that
;; we felt it to be a productive example of the intent.
(let ((then (get-universal-time))
(now (progn (sleep 10) (get-universal-time))))
(>= (- now then) 10))
=> true